Interesting thread.

In the case of my 1914 Ithaca Flues 20 ga., 2 different gunsmiths have verified that the chambers were at some point lengthend to 2 3/4". But one of the smiths commented that the chambers are "just barely 2 3/4" and not a fraction more". He also noted that the forcing cones were "short" and offered to lengthen them for me.

Since then, I've been fretting over shells and pressures. I can reload 2 3/4" 20 ga. shells at the lower end of the published spectrum, say under 8,500 p.s.i., but are such pressures low enough?

According to my reading, the "issue" with the 20 ga. version of the Flues is not chambers bursting, but it's lightweight frame cracking. There seems to be some debate out there as to whether the cracked frames are the result of excessive "pressure" or excessive "recoil". I, quite frankly, have not found a satisfactoty explanation of the difference between pressure and recoil, if in fact there is a difference.

I'm at the point now where I believe that I am over-thinking this whole matter of chambers, cones and pressures. I need to start enjoying this gun with my low pressure 2 3/4" reloads, instead of continuing to worry about it.